1. Field of the Invention
The present invention relates to a magnetoresistance effect head used as a reproducing head of a magnetic disk apparatus or the like, a fabrication method thereof, and a magnetic recording/reproducing head therewith.
2. Description of the Related Art
In recent years, the record density of magnetic recording apparatuses has been increased. High record density systems such as VCRs for 500 Mb/inch.sup.2 and HDDs for 200 Mb/inch.sup.2 have been commercially used. However, much higher record density is required for magnetic recording apparatuses. As a reproducing head for use with a high record density system, a magnetoresistance effect head using magnetoresistance effect of which an electric resistance of a magnetic thin film, a magnetic laminate, or the like varies corresponding to an external magnetic field is becoming attractive (hereinafter the magnetoresistance effect head is referred to as an MR head).
A conventional MR element using anisotropic magnetoresistance effect (hereinafter referred to as AMR) has an AMR film composed of a single layer of a NiFe alloy film or the like with a thickness of around 30 nm. To provide the AMR film with an operating point bias, an SAL bias film or the like is layered. The thickness of the bias film is around 20 to 30 nm. On the other hand, as a method for providing the AMR film with a longitudinal bias, an antiferromagnetic film such as a FeMn film is formed in a passive region other than a track portion.
FIG. 1 shows the structure of principal portions of an MR head having the conventional AMR film. As shown in FIG. 1, in the AMR element portion of the conventional AMR head, an AMR film 3 is layered on a laminate film composed of a soft magnetic film 1 and non-magnetic film 2 (namely, an SAL bias film) that provides an operating point bias. An antiferromagnetic film 4, which is a magnetic field providing film that provides a longitudinal bias, and a lead film 5, which is a conductor film composed of for example a Cu film that supplies a current to the AMR film 3, are formed in a passive region other than a track portion 3a. In other words, the width of the track portion 3a is defined corresponding to the pattern shape (lead shape) of the lead film 5.
As a patterning method of the above-described lead film 5, a lift-off method or an ion milling method is used. In the lift-off method, a resist is patterned as the negative pattern of the leads. Thereafter, the lead film 5 is formed by a sputter method, an evaporation method, or the like. In this case, the sputter method is preferable from view points of the cost and adhesive force. However, in the case that the sputter method is used, when the resist is peeled off with an organic solution such as acetone, the lead film 5 tends to be burred at the pattern edge portions. For example, in the case of a shield type AMR head, the burrs at the edge portions of the lead film 5 result in an insulation defect against an upper shield layer. Particularly, in an AMR head with an improved line resolution for a high record density of a recording medium (namely, an AMR head having a gap forming insulation film disposed between the AMR film 3 and the upper shield layer), an insulation defect tends to take place against the upper shield layer.
On the other hand, in the ion milling method, a lead film 5 composed of a Cu film or the like with a thickness of 100 to 200 nm is patterned just on the front surface of the AMR film 3 or with a slightly over-milled portion. In this case, due to the distribution of the thickness of the Cu film, the surface oxidized condition, the distribution of the intensity of ion beam, and so forth, it is difficult to determine the end point of the ion milling portion. Thus, this method has a problem in quantitative fabrication.
Since a giant magnetoresistance effect (hereinafter referred to as GMR) was discovered, in recent years, attempts for applying a GMR element for an MR head have been made so as to further improve high record density of recording apparatuses. Conventionally, the GMR film has a sandwich structure composed of a magnetic film, a non-magnetic intermediate film, and a magnetic film or a laminate structure that is composed of a plurality of magnetic film/non-magnetic film portions. The thickness of each film is on the order of several nanometers. The number of layers of the GMR film is larger than that of the conventional single-layered AMR film. In addition, the thickness of each layer of the GMR film is thin.
FIG. 2 shows the structure of principal portions of a conventional GMR head having a GMR film that is referred to as a spin valve (see J. Appl. Phys. VOL. 75, 6385 (1994) and so forth). As shown in FIG. 2, a spin valve film 6 has a structure of which a non-magnetic intermediate film 9 is disposed between a pair of ferromagnetic films 7 and 8. On the other hand, an antiferromagnetic film 10 such as a FeMn alloy film is formed on the ferromagnetic film 8 so that they contact each other. As with the AMR head, a lead film 5 composed of Cu or the like is patterned on the antiferromagnetic film 10.
The direction of the magnetization of the ferromagnetic film 8 is fixed in the direction in parallel with the signal magnetic direction Hsig of the medium by the antiferromagnetic film 10. The direction of the magnetization of the other ferromagnetic film 7 is rotated by an external magnetic field (signal magnetic field). The direction of the magnetization of the ferromagnetic film 7 is in parallel with the direction of the sense current. An antiferromagnetic film (or a hard magnetic film) 11 is disposed at both lower edge portions of a stripe of the spin valve film 6 so as to prevent a magnetic wall from taking place on the ferromagnetic film 7 of which the direction of the magnetization thereof is rotated by the signal magnetic field. The antiferromagnetic film (or the hard magnetic film 11) provides a bias magnetic field. (For details, see Japanese Patent Laid-Open Publication Nos. 62-40610 and 60-59518.)
As shown in FIG. 3, in the GMR head having the spin valve film 6, when the signal magnetic field H is 0, the resistance R thereof is between high and low. Depending on whether the signal magnetic field H is positive or negative, the resistance R varies between high and low. When the directions of magnetization of the layers of the spin valve film 6 have a difference of 90 degrees, the operating point bias is not required.
When a patterned lead film 5 is formed on the GMR film such as the spin valve film 6, since the thickness of each layer (7, 8, and 9) of the spin valve film 6 is as small as several nanometers, it is difficult to determine the timing for stopping the milling process. Thus, it is further difficult to equally mill the substrate as with the case of the AMR film. As described above, in the lift-off method, burrs take place. In the shield type MR head for high recording density, an insulation defect against the upper shield layer takes place.
In the conventional fabrication process for the GMR head as shown in FIG. 2, a hard magnetic film 11 that provides a bias magnetic field is formed and patterned. Thereafter, a laminate structure GMR film such as the spin valve film 6 is formed, patterned, and striped. After that, the lead film 5 is formed and patterned. In the conventional fabrication process for the GMR head, three steps of PEP (Photo Engraving Process) are required. Thus, the fabrication process is complicated and the fabrication cost rises.
As described above, in the conventional MR head structure, when a shield type head with a narrow gap is fabricated, if the MR element portion is patterned by the lift-off method, the pattern edges are burred and an insulation defect tends to take place. On the other hand, in the ion milling method, especially when a laminate structure GMR film is used, it is difficult to stop the milling process. Thus, it is difficult to obtain the MR element portion with high accuracy and high yield. In addition, when the MR element portion having the GMR film or the like is fabricated, three steps of PEP process are required, thereby increasing the fabrication cost.